Rotary compressor or exhauster



J. JOHNSTON.

ROTARY COMPRESSOR 0R EXHAUSTER.

APPLICATION FILED JAN. 14, I918. 1 ,357,872, Patented Nov. 2, 1920.

3 SHEETS-SHEET I.

J. JOHNSTON.

ROTARY COMPRESSOR 0R EXHAUSTER.

APPLICATIONFILRD JAN. 14, 1918.

Patented Nov. 2, 1920.

ATTORNEYS J. JOHNSTON.

ROTARY COMPRESSOR 0R EXHAUSTER.

. V APPLICATION FILED !AN.14, 1918 1,357,872. I Patented Nov. 2,1920.

3 SHEETS-SHEET 3.

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UNITED STA'LES PATENT OFFICE.

J'OI-IN JOHNSTON, OF LONDON, ENGLAND.

Specification of Letters Patent.

Patented N 0v. 2, 1920.

Application filed January 14, 1918. Serial No. 211,878.

T 0 all whom it may concern Be it known that I, JoHN JOHNSTON, a subject of the King of Great Britain and Ireland, and residing at 1 Victoria street, London, S. TV. 1, England, have invented certain new and useful Improvements in or Relating toBotary Compressors or Exhausters, of which the following is a specification.

This invention relates to rotary conipressors or exhausters of the type comprising an inner rotary member having a passage at its periphery for the'gas operated upon, an outer member eccentrically surrounding the inner member and a centrifugally held body of liquid between the inner and outer members.

()ne object of the present invention is to provide an improved form of machine of the above character which shall be simplified as to its construction and considerably more cliicient in operation than machines of this kind as hitherto adopted.

The invention consists in a rotary compressor or exhauster of the type referred to in which the rotor is provided with one or more helical threads, interrupted or continuous, extending across the width of the member but for aportion only of its circumference.

The invention also consists in a rotary compressor or exl'iauster of the type above referred to in which the inner rotary member is provided with one or more helical threads or vanes, each of which extends through half or approximately half the circumference of the said member.

The invention also consists in a machine of the type referred to having one or more helical or other threads upon the periphery of the inner member extending across the face of said member but extending lengthwise for a quarter or approximately a quarter of the periphery of the member, shrouding plates or webs being provided at each side of such thread or threads and having therein the necessary inlet and outlet ports for the gas operated upon.

it further object of the invention is to provide improved means for maintaining constant or approximately so the amount of liquid within the machine, and the invention also consists in a machine of the type referred to having one or more overflow pipes formed with or secured to the outer member and projecting into the liquid space between the two members, such pipe or pipes being arranged in or approximately in the central vertical plane of the machine or in any other convenient position.

The invention also comprises the form of apparatus hereinafter described or indicated.

The accompanying drawings illustrate two forms of machine in accordance with the invention Figure l is a side elevation of one form of rotor;

Figs. 2 and 3 are a plan and a cross-sectional elevation of the rotor shown in Fig. 1;

Fig. 4 is a detail; while Figs. 5, 6 and 7 are similar views to Figs. 1, 2 and 3, showing a modified form of rotor.

Fig. 8 is a sectional elevation showing one form of the complete machine.

In carrying my'invention into effect in one convenient manner as illustrated in Figs. 1 to 4, I form my improved machine with an outer, preferably rotary, member 2' (Fig. 8), of any suitable construction and arranged in any convenient manner, the size and formation of which is dependent upon the particular practical requirements which the invention may be called upon to fulfil.

Within the outer member and eccentrically thereto I arrange my improved form of inner rotary member a which may comprise a helical thread or vane 7) upon its outer surface formed integral with the drum or rigidly secured thereon or thereto, the vane extending for one-quarter or approximately one-quarter of the circumference of the drum-like member, and in conjunction with such thread or vane and arranged upon each side thereof I provide a shrouding plate or web 0, both of which plates or webs extend for the full depth or height of the thread and which are provided respectively with the inlet and outlet ports (Z, c for the air or gas that is to be operated upon.

The shrouding plates may be held in position by suitable clamping means or they may be formed integral with the drum or rotary member, the latter being formed of channeled section, the side webs of which form the shrouding plates and the thread or helical vane may be formed with the rotor or fixed thereto in any suitable manner as, for example, by riveting to the side members or by dropping the same into saw-cuts formed in the side or shrouding plates and also to the requisite depth in the peripheral face of the inner member.

For the purpose of increasing the capacity materially exceeds of the machine I may, as shown, provide four of such vanes or threads which are adapted to sllghtly overlap one another at their ends, the inlet and outlet ports being correspondingly increased in number, and being so arranged that there is no possibility of an inlet port and the corresponding outlet port being both out of the liquid at the same time, so that there will be no premature escape of the air and gastrapped within the chamber or passage formed by the thread and the shrouding plates.

It will be clear that in operation the different compartments defined by the plurality of vanes or threads will be necessarily lilledand discharged during one revolution. Each compartment is in turn filled to its full capacity where the distance between the liquid piston and the periphery of the rotor is the greatestand the sum total of the holding capacities of the different compartments the holding capacity of the crescent-shaped space defined by the rotor and the liquid piston. While by the use of a single thread making a complete convolution no greater olume can be transferred during one revolution than the volume that may be contained in the crescent space re ferred to, the volume that may be transferred by an apparatus of the construction described is nearly equal to the volume that may be contained in an annular space whose cross-section is equal to the greatest crosssection of the crescent. In theory this condition could be reached by providing an infinite number. of compartments. Since this theoretical condition, however, can for practical reasons not be attained and the gain in transfer capacity is very small over and above that construction in which a relatively small number of compartments is used, I find that fourvanes defining four compartments is the best compromise between a singlethread of the prior art and a large number of vanes. V 7

Owing to the fact that the inlet and outlet ports are arranged at, or approximately at, the ends of a diameter of the rotor, the time for which any given body of gas re mains in the machine is much reduced, being only the time'necessary. for the rotor to complete one half revolution, so that the time capacity andefliciency of the machine are very materially increased.

It will be clear, that the machine will opcrate with a single thread extending for ap proximately only a quarter of the periphery provided that the ports are approximately a half turn apart. 7

It is also obvious that the present construction brings about a better balancing of the compressor and thereby a, better distribution of the forces for operating it.

For the purpose; of increasing the chiciencyi oftheapparatus and improving its operation I prefer to provide an inclined portion f formed upon one of the shrouding plates, or a curved thickened portionat the root of the thread, suchextending for approximately one ing preferably of a decreasing thickness from one end of the thread to the other, such inclined or thickened portion in some cases being throughout its length conveniently curved or rounded on one side in cross-section, such rounded side or inclined portion being toward thedischarge side of the rotating member, so that at the termination of the thread it causes a gradual rise of the chamber up to the discharge port.

The usual paddles g'may or n ay not be provided in connection with the inner rotary member for the purpose of assisting the action of centrifugal force upon the, annular liquid piston, and any other accessories or appurtenances that may be considered usual or (lClfZlblQ may also be employed in my improved machine.

The threads may either follow a true helical path or they may be curved and merged into the shrouding plates or otherwise conveniently arranged to suit any particular requirements.

In machines of the character to which the invention relates it is generally desirable to maintain constant, or approximately so, the volume of liquid within the machine, and

for this purpose I may providein, or approximatelyin, the central vertical plane of the machine or in any other convenient position, one or more overflow pipes in projecting into the space between the members and carried by the outer member and adapted to discharge preferably into a peripheral channel carried by the outer member 7?, such pipes being of such a length that any excess liquid over the amount which is required in the machine overflows into the said pipes and is discharged therefrom under the action of centrifugal force, it being found that such. an arrangement is in some cases preferable to one in which a curved pipe or scoop is arranged at the side ofthe machine, inasmuch as the vacuum or pressure within the machine tends to distort the surface of the liquid piston in such a manner that the maximum distortion is at the center, and it is for thisireason that my outlet, pipes are arranged atthe point of maximum distortion. I

Also, in place of making the threads continuous I may, as shown in Figs. 5 to 7, interrupt the same with portions h. parallel to the sideplates, the remaining construction being similar to that above described. it is to be understood that the invention may be applied. alike to machines that are to be employed as compressors as to exhausters, and the methodfof providing for the distribution of the air or gasoperated upon as,

quarter of a turn, it be-' for example, by the use of hollow shafts or otherwise, may be modified in any suitable manner, as may also the means for supplying liquid to the machine and for maintaining the amount of liquid within the machine constant should such uniform supply be considered necessary or desirable.

Having now described my invention, what I claim as new and desire to secure by Letters Patent is 1. A rotary compressor or exhauster of the type referred to in which the rotor is provided with a helical thread extending across the width of the member but for a portion only of its circumference, substantially as described.

2. A rotary compressor or exhauster of the type referred to in which the rotor is provided with a plurality of helical threads, each of which extends across the width of the member but'for a portion only of its circumference, substantially as described.

3. A rotary compressor or exhauster of the type referred to in which the rotor is provided with a plurality of interrupted helical threads each of which extends across the width of the member but for a portion only of its circumference, substantially as described.

4;. A rotary compressor or exhauster of the type referred to in which the rotor is provided with a helical thread extending across the width of the member but for approximately a quarter of the circumference of said member, substantially as described.

. 5. A rotary compressor or exhauster of the type referred to in which the rotor is provided with a plurality of helical threads each of which extends across the face of the member but for approximately a quarter of the circumference of the said member.

6. A rotary compressor or exhauster of the type referred to comprising a rotor, a

at each sideof the said member having therein the necessary inlet and outlet ports for the gas operated upon, substantially as described.

7. A rotary compressor or exhauster of the type referred to comprising an outer casing, an inner rotor arranged eccentrically thereto, a body'of liquid in the space between the outer casing and rotor, a plural ity of helical threads. upon said rotor, each extending across the width of said member but through aportion only of the circumference of said member, shrouding plates at each side of said member having the necessary inlet and outlet ports for the gas operated upon and an overflow pipe secured to the outer member and projecting into the liquid space between the two members, sub stantially as described.

8. A rotary compressor or exhauster of the type referred to comprising an outer casing, an inner rotor member arranged eccentrically thereto, and. having a helical passage extending across its width and for a portion of its circumference for the gas operated upon, and a body of liquid in the space between the outer casing and the rotor substantially as described.

9. A rotary compressor or exhauster comprising an outer casing an inner rotary member having a helical passage extending across its width and for a portion of its circumference and of gradual decreasing area and a body of liquid in the space between the said casing and the said rotor.

In testimony whereof Ihave signed my name to this specification.

JOHN JOHNSTON. 

